Really, it comes down to sentimentality. When I first began studying Japanese, this was the first kanji I learned, and I made sure to learn it well, as I was always getting in trouble. Over time, I found that it doesn't carry the same playful and whimsical connotations as it does in English. This didn't stop me from adopting it as my online handle for countless games and services. Chances are, if you see a Komaru online in a game or some such, it's me. I also like the symmetry of the piece. Or rather, the deceptive asymmetry. When written out by hand, 木 is not perfectly symmetrical, but looks close enough to give the appearance of being so. It's been weird though, now that I live in Japan. For so long this Kanji has been a unique identifier to me, and now I see it on signs and in textbooks. It's a bit like seeing your name somewhere unexpected, it can be kind of jarring. Still it's all a good time, and it's definitely my favorite kanji.